Absorbent article comprising a liquid-permeable material layer

ABSTRACT

An absorbent article includes at least one liquid-permeable layer material ( 105 ) and an absorbent structure ( 106 ), the absorbent structure ( 106 ) having the ability to expand on wetting, which entails that the absorbent structure ( 106 ) displays a first volume in dry condition and a second volume in completely expanded wet condition, the second volume being greater than the first volume. The liquid-permeable layer material ( 105 ) encloses the absorbent structure ( 106 ) so that the absorbent structure ( 106 ) is prevented from reaching complete expansion during wetting.

TECHNICAL FIELD

The present disclosure concerns an absorbent article comprising aliquid-permeable surface layer and a liquid-impermeable surface layerand also an absorption body arranged between the surface layers, theabsorption body comprising at least one liquid-permeable material layerand an absorbent structure, the absorbent structure having the abilityto expand on wetting, which entails that the absorbent structuredisplays a first volume in dry condition and a second volume incompletely expanded wet condition, the second volume being greater thanthe first volume.

BACKGROUND ART

Absorbent articles such as diapers, incontinence protectors and sanitarynapkins are intended to receive and absorb body fluids such as urine andmenstrual fluid. Of course, articles with different forms and sizesexist depending on the area of use and the amount of fluid the articlemust be able to absorb. For example, diapers for heavily incontinentadults are considerably larger and have greater absorption capacity thandiapers for babies. Furthermore, in addition to the requirements forsufficient absorption capacity and leakage security, there is also arequirement that the diaper be comfortable to wear. For adult users itis also important that the articles are discreet and can be worn withoutbeing noticed under normal clothing. A further important criterion forabsorbent articles intended for single use is that they do not take uptoo much space during storage, transport and in the package bought bythe consumer.

In order to obtain a sanitary napkin which has a good fit, it is knownto produce articles with a three-dimensionally formed, anatomicallyadapted form. Absorbent articles which comprise shape-stable stiffmembers are described in SEA-9604223-9 and SE-A-9604221-3. Theshape-stabilising members, or forming members, are three-dimensionallyformed members constructed from materials which resist wrinkling orflattening when they are subjected to forces from the user's body, forexample when the user walks or sits on the article. Although thethree-dimensional shape solves the problem of obtaining a good fitduring use of the absorbent articles, three-dimensional absorbentarticles entail considerable difficulties during manufacturing andstorage. Three-dimensional parts are difficult to handle in amanufacturing process, for example when they have to be assembled tomake an absorbent article.

EP 0 834 296 A1 concerns an absorbent article which is flat in drycondition but which expands on wetting to a pre-determined,three-dimensional profile. The absorbent article has an expanded layer,preferably a foam of regenerated cellulose, i.e. viscose foam.Furthermore, the absorbent article has a liquid-permeable surfacematerial. The liquid-permeable surface material has pleats in drycondition, which pleats unfold on wetting so that the expanding layercan swell to several times its dry volume. However, a problem with suchan article is that viscose foams are very soft after being wetted. Afurther problem with the known article is that viscose foams have aninsufficient liquid-retaining ability.

SUMMARY

The disclosure therefore aims to remedy the problems with the previouslyknown expanding articles. A particular aim of the invention is toachieve an absorbent article with a shape-stable three-dimensionalstructure.

An article of the type described in the introduction has been achieved.The article enables an efficient use of the absorption capacity of aswellable absorbent article in order to give a better fit and tominimise the occurrence of leakage.

The absorbent article comprises at least one liquid-permeable layer andan absorbent structure, the absorbent structure having the ability toexpand on wetting and having a first volume in dry condition and asecond volume in completely expanded wet condition, the second volumebeing greater than the first volume. An absorbent article is chieflycharacterised in that the liquid-permeable material layer constitutesvolume-limiting means for the absorbent structure so that the absorbentstructure is prevented from reaching complete expansion on wetting.

In this way, the stiffness of the absorbent structure increases when itis wetted, whereby the swelled absorbent structure with thevolume-limiting means in wet condition forms a shape-stable formingelement. An advantage of such an article is that it is flat beforewetting, but that it displays a more three-dimensional form when it iswet.

The liquid-permeable material layer thus defines and limits theavailable expansion space for the absorbent structure. The materiallayer can be in the form of a continuous material layer which isarranged around the absorbent structure in such a way that completeexpansion of the absorbent structure is prevented. Alternatively, thematerial layer can be in the form of two or more material layers whichhave been joined together to make a surrounding sleeve around theabsorbent structure. It is also possible to arrange the absorbentstructure in a space between the liquid-permeable material layer and oneof the other components in the absorbent article, for example one of thecover layers of the article. It is not necessary that the expansionspace is completely closed around the absorbent structure. For example,elongated absorbent structures can be enclosed in tube-shaped sleeves orother spaces with open ends or open parts. What is essential is thatswelling of the absorbent structure is limited in the desired swellingdirection and in the desired parts of the absorbent structure.

By adapting the size and shape of the liquid-permeable material layer inrelation to the size and shape of the absorbent structure, it ispossible to predetermine the swelled/expanded form of the absorbentstructure and thus give the absorbent article a three-dimensional formwhich is adapted to the user's body, or which gives the article raisedbarriers or other three-dimensional functional elements.

Due to the fact that the liquid-permeable material layer limits theexpansion space of the absorbent structure, the absorbent structure,after wetting, will press against the liquid-permeable material layerand keep it expanded in the desired predetermined form. The expansionforce in the absorbent structure also entails that the forming elementformed on wetting exerts a counterforce when the forming element issubjected to compressive forces during use, for example when the userwalks or sits down. This means that a formed forming element has anextremely good ability to resist undesired compression or otherdeformation.

A further advantage with an article of this type is that the absorbentarticle is flat during the manufacturing process. As has been mentionedabove, three-dimensional parts are difficult to handle in amanufacturing process, for example when they have to be put together tomake an absorbent article.

In addition, it is an advantage that the absorbent article is flatbefore use as it is thus easier to package and occupies a smaller spacein the packaging.

According to one embodiment, the absorbent structure, after wetting,forms a forming element which is shape-stable. This means that theforming element is not deformed by the compressive forces acting in thearticle, which forces arise during normal use of the article, i.e. whenthe user sits, lies, stands or moves with the article in contact withhis/her body. An advantage of such an article is that the absorbentstructure, after wetting, forms one or several shape-stable, stiffmembers, which resist wrinkling or flattening when they are subjected toforces from the user's body. The forming element can, for example, forma raised portion on the surface which is covered by the liquid-permeablesurface layer or constitute an internal shape-stable element in theabsorption body.

According to a further embodiment, the absorbent structure can expandwhen wetted to a maximum volume which is ⅔ of the second volume of theabsorbent structure. In order to achieve a good effect from theexpansion restriction, the absorbent structure should have an expansioncapacity which is 100%-5000% and preferably 200%-4000%. Expansioncapacity denotes the ability of the absorbent structure to increase involume when taken from dry condition to wet condition without expansionlimitation. The expansion capacity can be determined, for example, withthe Volume Increasing Method described below.

The absorbent structure is advantageously a polyacrylate-based foammaterial. A polyacrylate-based superabsorbent foam material ismanufactured by saturating a solution consisting of at least monomers,crosslinkers, initiators and tenside and pressurising it with carbondioxide in a receptacle while stirring. When the solution is removedfrom the receptacle through a nozzle, the solution expands and a foamedstructure is obtained. The foamed structure is then locked due topolymerisation and crosslinking being initiated by means of, forexample, UV-radiation. Finally, the material is compressed and dried. Apolyacrylate-based foam of this type is described in detail in Example1.

Another type of absorbent structure which can be used comprises amixture of superabsorbent material and fibres. Superabsorbent materialdenotes absorption material with the ability to take up and bind liquidcorresponding to several times its own weight while forming a swelledhydrogel. The fibres preferably comprise absorbent fibres, such ascellulose fluff pulp, viscose fibres, cotton or the like. It is alsopossible to use mixtures of non-absorbent fibres and absorbent fibres,or only non-absorbent fibres. Non-absorbent fibres are, for example,various types of synthetic fibres of polymers, such as polyolefines,polyester and polyamide.

It is also possible to use pure cellulose fibre structures with highdensity. For example, an absorbent structure of cellulose fluff pulpwith a density of at least 0.3 g/cm³ can be used. The density of thecellulose fibre structure is determined on a rectangular materialsample, wherein the weight, area and thickness of the material aremeasured and the density is calculated from the measured values. Thethickness of the sample is determined at a pressure of 0.5 kPa. Allmeasurements are carried out at 23° C. and 50% relative humidity.

The liquid-permeable material layer can consist of or comprise anonwoven material. The liquid-permeable material layer can also consistof or comprise an apertured plastic film or a net material.

According to one embodiment, the absorbent article has two longitudinalside edges, wherein the absorbent structure, after swelling, formsraised liquid barriers arranged along the longitudinal side edges. Oneadvantage of such an embodiment is that the absorbent structure, afterthe first wetting, acts as raised liquid barriers. A further advantageof such an embodiment is that the absorbent structure has the ability,even on the first wetting, to prevent fluid leakage along thelongitudinal side edges due to the fact that fluid is taken up andstored by the absorbent structure.

A problem that is connected to conventional elasticated leakage barriers(“standing gathers”) which are intended to form pockets for gatheringliquid is that they can be compressed and flattened when they aresubjected to excessive external pressure. When the elastic barriers arecompressed, the pockets are more or less closed whereupon the liquid isprevented from flowing in to the pockets and instead runs over thebarriers. The described problem with conventional elasticated leakagebarriers is eliminated with the raised liquid barriers since theabsorbent structure forms, after wetting, a permanent raised portionwhich is essentially shape-stable.

According to another embodiment, the absorbent article has a thicknessdirection, the absorbent structure having an acquisition area forreceiving body fluid, consisting of at least a cavity or an area withlower density than a part of the absorbent structure that is adjacent tothe acquisition area and is situated chiefly on the same plane. The partthat is adjacent to the acquisition area comprises the absorbentstructure, wherein the absorbent structure chiefly increases in diameterin the thickness direction of the article during wetting and the size ofthe acquisition area increases in this direction during wetting. In thisway, a cavity, or a well, is formed, which has the ability to take upliquid during subsequent wettings.

According to a further embodiment, the absorbent structure, in drycondition, has a density that is at least 0.5 g/cm³. According to asimilar embodiment, the absorbent structure; in dry condition, has adensity that is at least 0.7 g/cm³. An advantage of an embodiment likethis is that the superabsorbent foam is thin before wetting.

The dry density denotes the density that the absorbent structure has inthe absorbent article during storage of the absorbent articles, forexample in a sealed diaper package. Diaper package refers to the packagein which the diapers are enclosed for sale. In some cases, diapers canbe individually wrapped, a number of individually wrapped diapers thenbeing sealed in a larger diaper package. Diaper package then does notrefer to the individually wrapped diaper but to the larger, outer diaperpackage. Similarly, if the absorbent article is an incontinenceprotector or a sanitary napkin, the density referred to is the densitythat the absorbent structure has in the absorbent article during storageof the absorbent articles in the sealed incontinence protector packageor the sealed sanitary napkin package. When the density of the absorbentstructure is measured, the measurement should be carried out within 2minutes from the packaging being opened. The density should be measuredwith a load of 0.5 kPa on the material.

According to a further embodiment, the total absorption capacity percubic centimeter of the absorbent structure in dry condition is at least15 g/cm³. According to a more preferred embodiment, the total absorptioncapacity per cubic centimeter of the absorbent structure in drycondition is at least 27 g/cm³. According to an even more preferredembodiment, the total absorption capacity per cubic centimeter of theabsorbent structure in dry condition is at least 35 g/cm³ Example 2describes in detail how the absorption capacity in the absorbentstructure is measured.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described below in more detail with reference tothe figures shown in the attached drawings, in which

FIG. 1 shows a sanitary napkin in accordance with an embodiment of theinvention,

FIG. 2 a shows a cross section along the line II-II through the sanitarynapkin in FIG. 1 after wetting,

FIG. 2 b shows a cross section along the line II-II through the sanitarynapkin in FIG. 1 before wetting,

FIG. 3 shows a diaper with liquid barriers in accordance with anembodiment of the invention

FIG. 4 shows a cross section along the line IV-IV through the diaper inFIG. 3,

FIG. 5 shows an incontinence protector with a forming element consistingof an absorbent structure in accordance with an embodiment of theinvention,

FIG. 6 shows a cross section along the line VI-VI through theincontinence protector in FIG. 5,

FIG. 7 shows a cross section through a test body for determination ofswelling,

FIG. 8 shows a schematic picture of a test arrangement for measurementof stiffness,

FIG. 9 shows Diagram 1,

FIG. 10 shows Diagram 2

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The sanitary napkin 100 shown in FIG. 1 comprises a liquid-permeablecover layer 101 arranged on the side of the sanitary napkin that isintended to be facing towards the user during use. Examples ofliquid-permeable cover layers 101 that can be used are various types ofnonwoven material, perforated plastic films, nets, or laminates ofthese.

The sanitary napkin 100 further comprises a backing layer 102 arrangedon the side of the sanitary napkin that is intended to be facing awayfrom the user during use. The backing layer 102 is suitably essentiallyliquid-impermeable or completely liquid-impermeable.

The liquid-permeable cover layer 101 and the backing layer 102 aremutually joined and form a projecting joining edge 103 around theperiphery of the sanitary napkin. The join between the layers can beachieved with any known technique suitable for the purpose, such asgluing or welding with heat or ultrasound.

Between the liquid-permeable cover layer 101 and the backing layer 102in a direction from the liquid-permeable cover layer 101 towards thebacking layer 102, there is a forming element 104, which is shown inswelled and unswelled condition (FIGS. 2 a and 2 b, respectively), andan absorption body 107.

The sanitary napkin 100 has an elongated form with a front transverseend edge 113, a rear transverse end edge 114 and two longitudinal sideedges 115, 116. The sanitary napkin 100 can also be divided into threeportions with regard to how the sanitary napkin is to be worn inrelation to a user's body. Thus, the sanitary napkin has a front endportion 111, a rear end portion 112 and a crotch portion 110 situatedbetween the end portions 111,112.

A fastening member 108 in the form of a longitudinal rectangular area ofself-adhesive glue is arranged on the surface of the backing layer 102that faces away from the user. The fastening member 108 extends overmost of the surface of the backing layer 102 between the two end edges113, 114. Before use, the fastening member 108 is suitably covered by areleasable protective layer, for example of siliconised paper.

It is possible, of course, to use other glue patterns than that shown,such as for example longitudinal stripes, transverse areas, dots orother figures. In addition, the type of fastening member has of courseno significance for the invention, it being possible to use frictionfastening and various types of mechanical fastening devices, such aswings or the like, alone or in combination with one another. It is alsopossible to dispense altogether with the use of fastening devices.

The extension and location of the forming element 104 correspond on thewhole with the form and size of the crotch portion 110 of the sanitarynapkin 100. The forming element 104 is constituted by a liquid-permeablematerial layer 105 and an absorbent structure 106, the absorbentstructure 106 having the ability to expand when wetted, with the resultthat the absorbent structure 106 has a first volume in dry condition anda second volume in completely expanded wet condition, the second volumebeing greater than the first volume. The liquid-permeable cover layer105 surrounds the absorbent structure 106 so that the absorbentstructure 106, when wetted, is prevented from reaching completeexpansion. It is essential that the liquid-permeable cover layer 105 isarranged around the absorbent structure 106 in such a way that theexpansion space is limited by the material layer 105. This can beachieved, for example, by the material layer 105 being in the form of aseamless tube, or having been made into a tube by joining two edges ofan initially flat material layer. It is also possible to achieve alimited expansion space by attaching the material layer 105 to anothercomponent, for example, the absorption body 107.

Due to the fact that the expansion space is limited, the absorbentstructure 106, after wetting, forms a raised portion which isessentially shape-stable, whereby the sanitary napkin 100 is notdeformed by the pressure forces acting in the napkin 100, which occurduring normal use of the napkin 100. The forming element 104, afterwetting, has a predetermined three-dimensional form with a centralraised portion 119 extending in the longitudinal direction of thesanitary napkin. During use of the sanitary napkin 100, the centralraised portion 119 shall be in contact with the user's body and shall bepartly inserted between the user's outer labia.

The central raised portion 119 has a longitudinal shape and becomesnarrower towards the end portions 111, 112 of the sanitary napkin 100.The raised portion is highest at the area which is intended to bearranged at the user's vaginal opening during use.

The absorption body 107 is arranged between the forming element 104 andthe backing layer 102. The absorption body 107 is suitably constitutedby one or several layers of some conventional absorption material.Examples of materials which can be used are tissue layers, waddinglayers of synthetic or natural fibres, layers of cellulose fluff pulp,absorbent foam layers or the like.

Examples of materials for the absorbent structure are polyacrylate-basedfoam materials.

FIG. 2 a shows in cross section how the forming element 104 appears whenthe absorbent structure 106 is wet and has swollen so that it fills theavailable expansion space inside the liquid-permeable material layer105. Due to the fact that the absorbent structure 106 cannot expandfreely but is limited by the liquid-permeable material layer 105, thislayer is held stretched out so as to form a shape-stable, stiff raisedportion 119 with low compressibility at the surface of the sanitarynapkin 100 that is intended to be in contact with the user's body duringuse. The shape of the raised portion 119 is determined by the shape ofthe available space which is defined by the liquid-permeable cover layer105.

FIG. 2 b shows an example of how the forming element 104 and theliquid-permeable cover layer 105 can be arranged before wetting. Theliquid-permeable cover layer 105 has a folded part 109 which can openout when the absorbent structure 106 swells. An alternative orcomplementary way to obtain expansion space is by forming theliquid-permeable cover layer 105 from an extensible material withlimited and predetermined extensibility. In both cases the expansionspace must be adapted so that the absorbent structure cannot expandcompletely.

The diaper 300 shown in FIGS. 3 and 4 has a conventional basicconstruction and comprises a liquid-permeable cover layer 301, aliquid-impermeable backing layer 302 and an absorbent body 307 arrangedbetween the liquid-permeable cover layer 301 and the liquid-impermeablebacking layer 302. The liquid-permeable cover layer 301 is suitably asoft, skin-friendly and pliable material of nonwoven, perforated plasticfilm, net, or the like. It is common to use polymer materials which arein themselves hydrophobic but which have been treated to obtain ahydrophilic surface so that liquid can pass through the layer. Ahydrophilised surface material of this type is advantageous because itdoes not absorb liquid and thus retains a dry surface. Various types oflaminates and combinations of different nonwoven layers and/or plasticfilm layers can also be used. A thin plastic film is usually used as theliquid-impermeable backing layer 302 but it is also possible to uselaminates and combinations of plastic films and nonwoven, hydrophobicnonwoven materials, or the like. It is an advantage if the backing layerhas a certain breathability so that air and water vapour can passthrough the layer.

The absorption body is also of conventional type and can thus consist ofone or several layers of absorbent material, for example cellulose fluffpulp with or without the addition of superabsorbents. The absorptionbody can also comprise liquid-acquisition layers, liquid-distributionlayers, stabilising members, binding agents, etc.

The diaper 300 has an hour-glass form with a longitudinal direction anda transverse direction and can be divided in the longitudinal directioninto a broader front portion 311 and rear portion 312 and also anintermediate narrower crotch portion 310. In addition, the diaper has afront transverse end edge or waist edge 313, a rear transverse end edgeor waist edge 314, and two longitudinal side edges 315, 316.

To enable the diaper to be fastened together into a pant shape aroundthe lower part of the user's torso, the diaper is provided with twofastening tabs 317, 318 arranged projecting from either side edge 315,316, parallel with the rear waist edge 314.

When the diaper 300 is put on, it is arranged with the front portion 311over the user's stomach, the rear portion 312 over the user's buttocksand the crotch portion between the user's legs. The diaper 300 is thenfastened together around the user's waist by the fastening tabs 317, 318being taken over the front portion 311 and fastened on a reception area320 on the outside of the front portion 311. The fastening tabs can beadhesive tape tabs, or comprise one part of a hook-and-loop fasteningarrangement. It is most common that the fastening tabs are provided withthe hook members of the hook-and-loop fastening arrangement and that thereception area has the corresponding loop members. These can be in theform of a nonwoven material with fibre loops into which the hook memberscan hook. If the outer surface of the diaper consists of such a nonwovenmaterial, no particular reception area is required. In the same way, aparticular reception area for adhesive fastening tabs can be dispensedwith if the outer surface is a plastic film which in itself hassufficient strength to bear fastening and preferably also opening andreclosing of the tape tabs.

The shown fastening member in the form of fastening tabs 317, 318 is ofcourse not necessary for the invention, it being possible to use othersuitable fastening members such as belts, buttons, hook-and-eye, or thelike.

In order to give a good fit and to increase leakage security, the diaper300 is provided with leg elastic 321, 322 in the form of elastic threadsor bands which are arranged pre-stretched along those parts of the sideedges 315, 316 which form leg openings when the diaper 300 is worn. In acorresponding manner, an elastic band or the like is arranged along therear waist edge 314 and forms waist elastic 323. The diaper 300 is shownin the figures with the elastic members 321, 322, 323 in stretchedcondition. When the stretching ceases, the elastic is drawn together andgives the diaper a three-dimensional form with wrinkled edges.

The diaper also has two longitudinal liquid barriers 324, 325 arrangedin the longitudinal direction on either side of a central liquidacquisition area 326 on the diaper. The liquid barriers each comprise aliquid-permeable material layer 305 which has been formed into a tunnelaround an absorbent structure 306, as can be best seen in FIG. 4. In theshown example, the barrier tunnels are formed in separate materialstrips which are fastened, for example, with glue or ultrasound weldingon the surface 301 of the liquid-permeable cover layer. Alternatively,it is possible to form the barrier tunnels in the liquid-permeable coverlayer 301 and to exclude the specific material strips.

The liquid barriers 324, 325 are constituted by a liquid-permeablematerial layer 305 and an absorbent structure 306, the absorbentstructure 306 having the ability to expand when wetted, with the resultthat the absorbent structure 306 has a first volume in dry condition anda second volume in completely expanded wet condition, the second volumebeing greater than the first volume. The liquid-permeable cover layer305 surrounds the absorbent structure 306 so that the absorbentstructure 306, when wetted, is prevented from reaching completeexpansion. It is essential that the liquid-permeable cover layer 305 isarranged around the absorbent structure 306 in such a way that theexpansion space is limited by the material layer 305. This can beachieved, for example, by the material layer 305 being in the form of aseamless tube, or having been made into a tube by joining two edges ofan initially flat material layer. It is also possible to achieve alimited expansion space by attaching the material layer 305 to anothercomponent.

Due to the fact that the expansion space is limited, the absorbentstructure 306, after wetting, forms a portion which is essentiallyshape-stable, whereby the absorbent structure 306 is not deformed by thepressure forces acting on the diaper 300, which occur during normal use.The liquid barriers 324, 325, after wetting, have a predeterminedthree-dimensional form extending in the longitudinal direction of thesanitary napkin.

In the shown example, the absorbent structure 306 extends only withinthat part of the diaper 300 which is situated around the leg openingswhen the diaper is being worn. Consequently, the absorbent structure 306is in the crotch portion 310 and extends a short distance into the frontportion 311 and the rear portion 312, respectively. The shown embodimentgives good leakage security with raised barriers around the leg edgesbut leaves the front and rear portions 311, 312 of the diaper smooth andin contact with the user's body during use.

Naturally, it is possible to arrange expanded barriers over a greater orsmaller part of the length of the diaper than that shown. It is alsopossible to arrange swellable barriers at the waist edges of the diaperor as liquid control members anywhere on the liquid-permeable surface ofthe diaper where it is desirable to direct the liquid flow. For example,it is possible to create channels in order to lead the liquid towardsthe end portions of the diaper by arranging parallel expandable barriersat the wetting area of the diaper, i.e. the part of the diaper that isintended to be wetted first by body fluids. When the user excretesliquid to the wetting area, the barriers swell up and form liquidtransport channels between them.

FIGS. 5 and 6 show an incontinence protector 500 comprising aliquid-permeable cover layer 501 and a liquid-impermeable backing layer502, which are mutually attached in a joining edge 503 and togetherenclose an absorption body 507 and a forming element 504. The formingelement 504 consists of a layer of an absorbent structure 506 which isenclosed between two liquid-permeable material layers 505′, 505″ whichhave been joined together, for example, by gluing or welding. Theforming element 504 is placed on the absorption body 507 between theabsorption body and the liquid-permeable cover layer 501 and serves as aliquid transfer member to the absorption body 507. The absorption body507 suitably consists of an absorbent material with high absorptioncapacity and retention ability, for example a mixture of cellulose fluffpulp and superabsorbents. Due to the absorbent structure 506 itselfhaving a good absorption ability, the absorption capacity obtained bythe forming element 504 can be sufficient for certain applications, forexample for incontinence protectors intended to be used for lightincontinence. In such an embodiment, the absorption body 507 can beexcluded, or formed as a thin security layer with low absorptioncapacity, for example a tissue material.

The incontinence protector 500 has an hour-glass shape with two endportions 511, 512 and an intermediate crotch portion 510, as well astransverse end edges 513, 514 and longitudinal side edges 515, 516.

Like the sanitary napkin 100 shown in FIGS. 1 and 2, the incontinenceprotector 500 is provided with an adhesive fastening member 508 on theoutside of the liquid-impermeable backing layer 502.

The forming element 504 is provided with a number of through holes 530,531. In the shown example, the holes go through both theliquid-permeable material layers 505′, 505″ and the absorbent structure506 but it is possible, alternatively, to arrange holes only through theabsorbent structure 506. The holes 530, 531 can have any suitable formand can also be in the form of channels. The number and size of theholes can also be varied. By selecting the location, size and mutualdistance of the holes, it is possible to achieve different degrees ofexpansion inhibition in different parts of the absorbent structure. As aresult, the absorbent structure has different stiffness in differentareas after swelling. In this way, it is possible to obtain a formingelement that has varying flexibility and therefore is formable ordeformable to varying degrees in different areas. Generally, openingsplaced close together give greater stiffness in the area between theopenings than openings spaced farther apart. It is therefore possible tocreate an absorbent article which adapts itself optimally to the bodyshape of the user due to the flexibility of the forming element.

Two oval holes 530 are arranged in the crotch portion 510 of theincontinence protector 500 and three circular holes 531 are arranged ateach end portion 511 on the incontinence protector. When liquid meetsthe incontinence protector 500 and is absorbed by the absorbentstructure 506, the absorbent structure swells in the thickness directionof the incontinence protector, as is shown in FIG. 6. The holes 530, 531thus form liquid acquisition wells which can function as temporaryreservoirs for liquid that has not yet been absorbed by the underlyingabsorption body 507. When the absorbent structure 506 expands, the spacebetween the liquid-permeable material layers 505′, 505″ is filled untilthese layers limit further. expansion. The stiffness in the expandedmaterial is thus increased so that the forming element 504, afterexpansion, also counteracts undesired, uncontrolled compression anddeformation of the incontinence protector. The location of the ovalholes 530 can mean that the holes can also serve as longitudinal bendingindications for the incontinence protector 500, so that the partsbetween the holes 530 and the side edges 515, 516 are folded up when theincontinence protector 500 is compressed between the user's legs duringuse. The crotch portion 510 of the incontinence protector thus obtains abowl shape adapted for liquid acquisition.

Therefore, it is possible to create a liquid-acquisition member whichalso serves as a forming member for an absorbent article during use.

The described embodiments shall not be considered to limit the inventionbut only constitute examples of applications of the invention. Theexpandable forming elements in the different embodiments can, of course,be used for other types of absorbent article than those described. Itis, of course, also possible to combine the different forming elementswith each other.

Example 1 Measurement of Expansion of Foam Material

When the expansion in the thickness direction of the material wasmeasured, samples were punched out with a known diameter. The drydiameter (d_(t)) and the dry thickness (t_(t)) were measured. Thesamples were then allowed to swell for 1 minute in NaCl solution (0.9weight percent NaCl). The wet diameter (d_(v)) and the wet thickness(t_(v)) were then measured.

The percentage thickness expansion (TE), the percentage area expansion(AE) and the percentage volume expansion (VE) were then calculatedaccording to the formulae below.TE=(t _(v) −t _(t))/t _(t)×100AE=(d _(v) ² −d _(t) ²)/d _(t) ²×100VE=(t _(v) d _(v) ² −t _(t) d _(t) ²)/t _(t) d _(t) ²×100The material which was tested is a polyacrylate-based foam which isdenoted Foam XII. Foam XII has been manufactured according to thedescription below.

The following was added to a beaker:

-   -   348.5 grams acrylic acid (4.84 mol)    -   135.5 grams of a 37.3 weight percent natrium acrylate solution        (0.54 mol)    -   28.0 grams polyethylene glycol diacrylate from polyethylene        glycol with a mol mass of 400.    -   21.3 grams of a 15 weight percent water solution that contains        ethylene oxide and linear C16C18 fat alcohol (mol ratio 80:1)    -   65.7 grams water

This was mixed. The solution was then cooled to a temperature under 16degrees Celsius. The solution was then poured into a sealed container,whereupon the solution was saturated with carbon dioxide gas at apressure of 12 bar for 25 minutes. Under the same pressure, 26.7 gramsof a water solution containing 3 weight percent of2,2′-azobis(2-amidinopropane)dihydrochloride was added. This was mixedto form a homogenous solution. The solution was then allowed to rest forfive minutes. The saturated solution was then pressed out of a containervia a nozzle with an opening that was 1 mm at a pressure of 12 bar.

The resulting monomer foam was placed on a glass plate (DIN-A3). Afurther glass plate was then placed over the monomer foam. Thereafter,the foam was polymerised with a UV/VIS lamp, a UV1000 lamp from theHönle company. The foam was illuminated with the lamp both from belowand above. The illumination, and thus the polymerisation, was allowed toproceed for 4 minutes.

Results for Foam XII:

d_(t) t_(t) d_(v) t_(v) TE AE VE 28 3.8 62 6 58 357 622 28 3.8 61 6 58390 577 28 3.8 62 6 58 390 649

The thickness expansion shall preferably be 40-80%, area expansion shallpreferably be 300-400% and the volume expansion shall preferably be500-800%.

Example 2 Absorption Capacity

The total absorption capacity per unit of volume of the absorbentstructure in dry condition was determined for five different samples.

Sample A is a mixed structure of chemically-produced cellulose pulp fromWeyerhauser and polyacrylate-based superabsorbent in particle form fromBASF. The mixed structure contains 40 weight percent superabsorbentmaterial, based on the total weight of the sample.

Sample B is a fibre structure from Weyerhauser. The fibre structurecontains 80 weight percent cross-linked cellulose and 20 weight percentthermofibres.

Sample C is a polyester fibre layer with polyacrylate-basedsuperabsorbent in particle form bound to the polyester fibre layer.Based on the total weight of the sample, the proportion ofpolyacrylate-based superabsorbent is 60 percent.

Sample D is a polyacrylate-based superabsorbent foam layer. The foamlayer is denoted Foam XII and is described in detail in Example 1.

Sample E is a viscose foam, i.e. a foam of regenerated cellulose.

The measurement was carried out by first weighing the dry sample. Thevolume of the dry sample is then obtained by dividing the weight of thedry sample with the density of the dry sample. The sample was thensaturated with a 0.9 weight percent NaCl-solution. The sample wasprovided with an excess of NaCl-solution and was allowed to absorb theliquid for 20 minutes. The saturated sample was then weighed. The amountof liquid which had been absorbed was obtained by subtracting the weightof the dry sample from the weight of the saturated sample.

The total absorption capacity, measured in grams of liquid per cubiccentimeter of the absorbent material in dry condition was as follows:

Absorption capacity (grams liquid/cm³) Sample ρ = 0.50 g/cm³ ρ = 0.71g/cm³ ρ = 0.91 g/cm³ Sample A 15 19 22 Sample B 6 6 8 Sample C 14 20 26Sample D 27 38 49 Sample E 14 20 26

The result clearly shows that Foam XII, i.e. sample D, has a greatertotal absorption capacity, measured in grams of liquid per cubiccentimeter of the absorbent material in dry condition.

Example 3 Stiffness of Sample Bodies with Limited Expansion Space

In order to investigate the change in the stiffness and thus the shapestability of the absorbent material which has been allowed to absorbliquid under conditions where the expansion ability of the absorbentmaterial has been limited in accordance with the invention, thefollowing test was carried out:

Sample bodies were produced from the various absorbent materials. Thesample bodies were rectangular with a width of 0.01 m and a thickness of0.0044 m. The length of the samples is not critical as long as itexceeds 0.04 m. The sample bodies were enclosed in a liquid-permeabletube-shaped nonwoven sleeve, as is shown in FIG. 7. The diameter of thesleeve 702 was chosen so that the sample 701 was left a certainpre-determined and limited expansion space defined by the length L_(w)of the excess material which is shown in FIG. 7 between one of the endsof the sample and a weld 703 arranged to fasten the sleeve into a tubearound the sample. As the thickness of the dry samples is negligible inthese circumstances, the length L_(w) gives a good measurement of theavailable expansion space.

12 samples were tested:

a) samples 1, 3, 5, 7, 9 and 11 consisted of a mixture of superabsorbentand chemical cellulose fluff pulp in the ratio 50/50 weight percent. Thecellulose fluff pulp was southern pine NB 416 from Weyerhauser and thesuperabsorbent was BASF 7160. The nonwoven material used as a sleevearound the sample bodies was a polypropylene spunbond material with abasis weight of 16 g/m² from BBA Nonwovens, France.b) samples 2, 4, 6, 8, 10, 12 consisted of Foam XII in accordance withExample 1 enclosed in a nonwoven sleeve of the same type as in a), i.e.a polypropylene spunbond material with a basis weight of 16 g/m² fromBBA Nonwovens, France.Test of Absorption Capacity and Volume of Enclosed SamplesI. Absorption Capacity:The dry sample was weighed: w₁Thickness and width of the dry sample were measuredThe sample was put in a dish with 0.9% NaCl solution and was allowed toabsorb for five minutesThe sample was removed from the liquid and weighed: w₂The sample was removed from the scale and the amount of liquid remainingon the scale was noted: w₃The amount of NaCl solution which had been absorbed in grams per gramwas calculated by subtracting the dry weight (w₁) of the sample and theweight of the liquid remaining on the scale (w₃) from the weight shownon the scale (w₂):Absorption (g/g)=(w ₂ −w ₁ −w ₃)/w ₁

Two sample bodies were tested for each sample.

The test results are presented in Table 1 (superabsorbent/pulp mixture)and Table 2 (superabsorbent foam).

TABLE 1 Dry width Weight Sample + nw Weight remaining Absorbed Dry Dryweight (L_(w)) after abs. on scale Weight Wet volume thickness Sample W₁(mm) W₂ W₃ (g/g) (cm³) (mm) 1-1 1.08 10 + 0 10.55 0.21 8.6 10 4.3 1-21.05 10 + 0 10.21 0.22 8.5 9 3-1 2.20 10 + 2 11.78 0.30 9.4 11 4.4 3-21.08 10 + 2 12.89 0.43 10.5 12 5-1 1.14 10 + 4 14.77 0.54 11.5 14 4.25-2 1.11 10 + 4 14.31 0.15 11.8 14 7-1 1.17 10 + 6 17.05 0.17 13.4 144.4 7-2 1.17 10 + 6 16.59 0.26 13.0 16 9-1 1.18 10 + 8 18.02 0.45 13.917 4.25 9-2 1.19 10 + 8 18.66 0.29 14.4 18 11-1  1.21  10 + 10 20.950.52 15.9 20 4.4 11-2  1.15  10 + 10 20.79 0.45 16.7 20

TABLE 2 Dry width Weight Weight Dry weight Prov + nw after abs.remaining Absorbed Dry W₁ (Lw) W₂ on scale weight Wet volume thicknessSample (g) (mm) (g) W₃ (g/g) (cm³) (mm) 2-1 0.78 10 + 0 7.69 0.60 8.1 73.4 2-2 0.76 10 + 0 6.91 0.18 7.9 7 4-1 0.77 10 + 2 8.84 0.24 10.2 9 3.44-2 0.78 10 + 2 8.52 0.13 9.8 8 6-1 0.81 10 + 4 10.99 0.10 12.4 11 3.46-2 0.78 10 + 4 12.48 0.32 14.6 12 8-1 0.80 10 + 6 12.54 0.38 14.2 123.4 8-2 0.84 10 + 6 13.63 0.39 14.8 13 10-1  0.82 10 + 8 16.55 0.50 18.616 3.4 10-2  0.82 10 + 8 14.89 0.34 16.7 15 12-1  0.86  10 + 10 18.490.91 19.4 18 3.4 12-2  0.89  10 + 10 17.93 0.81 18.2 18II. Volume Increase

The sample was prepared by being wetted by an excess of NaCl solutionfor 5 minutes so that the sample absorbs liquid and expands.

A 100 ml measuring glass was filled with 70 ml 0.9% NaCl solution.

The liquid-saturated, swelled sample bodies were lowered into themeasuring glass and the increase in volume was noted.

The method of measurement can be adapted according to the size of thesample. A larger or smaller measuring glass can be used, as can adifferent amount of liquid.

The volume increase in percent was calculated both based on the absorbedamount of liquid in grams/gram in accordance with method I, and based onthe determination of displaced liquid in accordance with method II. Ascan be seen from Table 3 and Table 4, the methods give comparableresults.

For the tested materials, complete expansion was reached when L_(w) was10 mm (10+10 in the tables) and essentially no expansion when L_(w) was0 mm.

TABLE 3 Calculation of expansion limitation Based on Based on Based onliquid Based on liquid g/g-increase displacement g/g-increasedisplacement mean value mean value Sample 49% 50% 49% 53% 1 49% 55% 43%45% 40% 43% 3 37% 40% 31% 30% 30% 30% 5 30% 30% 20% 30% 21% 25% 7 22%20% 17% 15% 15% 13% 9 13% 10%  5%  0%  2%  0% 11  0%  0%

TABLE 4 Calculation of expansion limitation Based on Based on Based onliquid Based on liquid g/g-increase displacement g/g-increasedisplacement mean value mean value Sample 58% 61% 59% 61% 2 60% 61% 48%50% 49% 53% 4 50% 56% 36% 39% 30% 36% 6 25% 33% 27% 33% 26% 31% 8 24%28%  4% 11%  9% 14% 10 14% 17%  0%  0%  3%  0% 12  6%  0%Determination of Stiffness

The stiffness/shape stability for the swelled samples was measured bydetermining the elasticity module for the samples with an Instron4301H1120, Software: Series IX.

The determinations of stiffness were carried out at 23° C. and 47%humidity.

The test arrangement is shown schematically in FIG. 8. The swelledsample 801 was laid on two supports 802 placed at the distance L=0.03 mfrom each other. The test was carried out with a compression speed of100 mm/min and the elasticity module E was calculated as a function ofthe compression force F and the curve d of the sample as follows:E=F×L ³ /d×48×I(N/m²)

Where I is the moment of inertia and L is the distance between thesupports 802.

Diagram 1 and Diagram 2 show the elasticity module E for the differentsamples as a function of the expansion limitation in percent. As can beseen in the diagrams, the elasticity module, and thus the stiffness ofthe sample, increases as the expansion space decreases.

Alternative Method for Estimating Expansion Inhibition; Test ofAbsorption Capacity for Enclosed and Opened Samples.

Weigh the dry, enclosed sample: w₁.

Lay the sample in a dish and add excess of 0.9% NaCl solution for fiveminutes.

Remove sample from liquid and weigh the wet sample: w₂

Remove sample from scale and note how much liquid remains on scale: w₃.

Calculate how much NaCl solution has been absorbed by the sample ingrams per gram by subtracting dry weight (w₁) of sample and weight ofremaining liquid (w₃) from weight shown by scale (w₂).Absorption (g/g): (w ₂ −w ₁ −w ₃)/w ₁

Weigh a polyester net, for example PE59HC from J.H. Tidbeck AB. This isa standard material which is used for different types of absorptiontests, for example in the so-called Teabag Method. The net should havesufficient size to be able to retain the completely swelled sample inthe liquid.

Cut open the sleeve/expansion-limiting material of the sample and placethe sample on the polyester net.

Lay the polyester net with the sample in a dish with 0.9% NaCl solutionand ensure that the sample has constant access to liquid. Let the sampleabsorb for five minutes.

Lift up the polyester net with the sample and weigh this: W₄.

Remove the sample from the scale by scraping the sample from the wetpolyester net and note the weight of the polyester net and the liquidremaining on the scale: w₅.

Calculate how much NaCl solution the open sample has absorbed in gramsper gram by subtracting the weight of the dry sample (w₁) and thepolyester net and the remaining liquid (w₅) from the weight (w₄) of wet,completely expanded sample and divide this by the weight (w₁) of the drysample.Absorption g/g=(w ₄ −w ₁ −w ₅)/w1.

The described method can be used, for example, to estimate the expansionlimitation in a sample which has been taken from an absorbent article.If it is only of interest to measure the full expansion ability of thesample, the first, volume-limiting swelling step can be excluded. Thesleeve of the dry sample is then cut open and placed directly onto apolyester net, whereafter the test is carried out with wetting andweighing as described above.

Samples Taken from Existing Absorbent Articles

For measurement of expansion limitation and stiffness in existingabsorbent articles, measurements can be carried out either on wholeexpansion-limited elements in the article or on parts of such elementswhere samples can be taken out of the article without destroying theexpansion-limiting means. For example, such a part element can be apiece of one of the raised, swellable liquid barriers 324, 325 in FIG.3, or the delimited and enclosed part between the oval holes 530 in FIG.5.

The invention is not limited to the embodiments described above andshown in the drawings, but may be varied within the scope of the claims,and equivalents thereof. In particular, the invention is not limited toa particular type of absorbent article, but the embodiments shown may beapplied to any type of absorbent article. Details from the differentembodiments may of course be combined as desired, as will be evident tothe person skilled in the art.

1. An absorbent article comprising a liquid-permeable surface layer anda liquid-impermeable surface layer and an absorption body arrangedbetween the surface layers, the absorption body comprising aliquid-permeable material layer and an absorbent structure, theabsorbent structure having the ability to expand on wetting and having afirst volume in a dry condition and a second volume in a completelyexpanded wet condition, the second volume being greater than the firstvolume, wherein the liquid-permeable material layer constitutes avolume-limiting device for the absorbent structure so that the absorbentstructure is prevented from reaching the completely expanded wetcondition on wetting in an excess of 0.9% NaCl solution for 5 minutesand so that the absorbent structure after wetting in an excess of 0.9%NaCl solution for 5 minutes has a greater stiffness than in the drycondition and thus forms a forming element in the absorbent article,wherein the absorbent structure expands to a mean value of 70% or lessof the completely expanded wet condition on wetting in an excess of 0.9%NaCl solution for 5 minutes, based on g/g increase.
 2. The absorbentarticle in accordance with claim 1, wherein the absorbent structure canexpand when wetted to a maximum volume which is ⅔ of the second volumeof the absorbent structure.
 3. The absorbent article in accordance withclaim 1, wherein the absorbent structure comprises a polyacrylate-basedfoam material.
 4. The absorbent article in accordance with claim 1,wherein the absorbent structure comprises a mixture of superabsorbentmaterials and fibres.
 5. The absorbent article in accordance with claim4, wherein the fibres comprise absorbent fibres.
 6. The absorbentarticle in accordance with claim 5, wherein the absorbent fibrescomprise cellulose fluff pulp.
 7. The absorbent article in accordancewith claim 1, wherein the liquid-permeable material layer comprises anonwoven material.
 8. The absorbent article in accordance with claim 1,wherein the liquid-permeable material layer comprises a perforatedplastic film.
 9. The absorbent article in accordance with claim 1, theabsorbent article further comprising two longitudinal side edges, andthe absorbent structure forms raised liquid barriers arranged along thelongitudinal side edges.
 10. The absorbent article in accordance withclaim 1, wherein the absorbent structure in the dry condition has adensity that is at least 0.5 g/cm³.
 11. The absorbent article inaccordance with claim 1, wherein the absorbent structure in the drycondition has a density that is at least 0.7 g/cm³.
 12. The absorbentarticle in accordance with claim 1, wherein the total absorptioncapacity per cubic centimeter of the absorbent structure in the drycondition is at least 15 g/cm³.
 13. An absorbent article comprising aliquid-permeable surface layer and a liquid-impermeable surface layerand an absorption body arranged between the surface layers, theabsorption body comprising a liquid-permeable material layer and anabsorbent structure, the absorbent structure having the ability toexpand on wetting and having a first volume in a dry condition and asecond volume in a completely expanded wet condition, the second volumebeing greater than the first volume, wherein the liquid-permeablematerial layer constitutes a volume-limiting device for the absorbentstructure so that the absorbent structure is prevented from reaching thecompletely expanded wet condition on wetting in an excess of 0.9% NaClsolution for 5 minutes and so that the absorbent structure after wettingin an excess of 0.9% NaCl solution for 5 minutes has a greater stiffnessthan in the dry condition and thus forms a forming element in theabsorbent article, the absorbent article further comprising a thicknessdirection, wherein the absorption body comprises an acquisition area forreceiving body fluid, the acquisition area comprising at least a cavityor an area with a lower density than a part of the absorption body thatis adjacent to the acquisition area and is situated chiefly in a singleplane, and the part that is adjacent to the acquisition area comprisesthe absorbent structure, wherein the absorbent structure forms a raisedbarrier arranged on each side of the acquisition area in a longitudinaldirection of the acquisition area, the absorbent structure chieflyincreases in diameter in the thickness direction of the article duringwetting and the size of the acquisition area increases in the thicknessdirection during wetting.